The ovaries are small, almond-shaped organs situated in the pelvic cavity. Their primary role is to produce the hormones estrogen and progesterone and to release an egg each month for potential fertilization. Measuring ovarian size, typically via ultrasound, is a standard way to assess reproductive health. Normal dimensions vary significantly throughout a person’s life, depending on age and the current physiological state of the reproductive system.
Typical Ovarian Size During Reproductive Years
During childbearing years, the ovaries are largest and most active, reflecting the continuous process of follicle development. Normal dimensions are approximately 3 to 5 centimeters in length, representing the longest axis of the organ.
The width typically ranges from 1.5 to 3 centimeters, and the thickness (anterior-posterior dimension) is usually between 0.6 and 1.5 centimeters. These dimensions result in a volume that typically falls between 3 and 6 cubic centimeters (cm³ or mL). The upper limit of normal volume for a premenopausal ovary is generally considered to be around 10 cm³. Ovarian volume is highest in the early twenties, peaking around 7.7 mL, and begins a gradual decline after the age of 30.
Physiological Size Changes Across the Menstrual Cycle
The ovaries do not maintain a static size throughout the month; they undergo natural, temporary enlargement driven by hormonal shifts. This cyclical change is a normal part of the menstrual process, involving follicular phase, ovulation, and a luteal phase. The development of the dominant follicle is the main cause of this size increase.
In the first half of the cycle, the dominant follicle grows daily, often increasing its diameter by 2–3 millimeters per day. Just before ovulation, this fluid-filled sac can reach a diameter of 1.8 to 2.7 centimeters, significantly contributing to the overall ovarian size. Following ovulation, the follicle transforms into the corpus luteum, which also temporarily adds to the ovarian volume. This structure produces progesterone and can cause the dominant ovary to maintain an increased size during the second half of the cycle before returning to baseline.
Ovarian Dimensions in Childhood and Post-Menopause
Ovarian size is significantly smaller during the non-reproductive phases of life, specifically childhood and post-menopause. In pre-pubescent girls, the ovaries are small and quiescent, often measuring less than 2 centimeters in length, with a mean volume typically less than 1 cm³ in girls under six years of age.
As a woman approaches and enters menopause, the ovaries undergo atrophy due to the cessation of hormonal production and follicular activity. After the ovaries stop releasing eggs, their size diminishes considerably, often shrinking to a length of 2 centimeters or less. The average volume for post-menopausal ovaries is significantly reduced, falling to an average of 2.2 cm³.
Common Causes of Ovarian Enlargement
When an ovary is measured as significantly larger than the normal baseline, it can be due to several non-physiological conditions. One common cause is the development of functional cysts, which are benign, fluid-filled sacs. Follicular cysts occur when the dominant follicle fails to rupture, continuing to grow and sometimes reaching several centimeters in diameter. Another frequent cause is Polycystic Ovary Syndrome (PCOS), where hormonal imbalance leads to enlarged ovaries with volume exceeding 10 cm³ due to multiple small, undeveloped follicles. Other factors causing measurable enlargement include endometriomas (cysts formed from endometrial tissue) and benign tumors. Persistent or significant enlargement warrants professional medical evaluation.